$\left[\begin{array} {ccc} -9\\ -4\\ -4\\ 5\\ 0 \end{array}\right]$ What are the dimensions of the matrix?
The first dimension is the number of rows in the matrix. There are $5$ rows. The second dimension is the number of columns in the matrix. There is $1$ column. In conclusion, the dimensions of the matrix are $5\times 1$.